Safety back pressure signal for flues



Nov. 17, 1959 O. MOBLEY SAFETY BACK PRESSURE SIGNAL FOR FLUES Filed March 14, 1956 E 39 a 30 a: l I A /9 {"1 -29 I 32w- I- .T'

' INVEN TOR.

A 0 Me ff W Y United States. Patent SAFETY BACK PRESSURE SIGNAL FOR FLUES Ora Mobley, Taylorsport, Ky.

Application March 14, 1956, Serial No. 571,468

2 Claims. (Cl. 158-122) The present invention relates to a heating system and particularly to an automatic control which will prevent the passage of combustion products from the fire in a space heater into the heated room because of the failure of a defective or inoperative chimney stack, or the stack connections, to conduct said products from the heater to the outside atmosphere.

The flue gas conducting passages in chimney stacks all too frequently are accidentally closed or restricted by foreign material such as loose bricks, flaked mortar and soot thus causing draft failure and the inability of the chimney to carry ofi the combustion gases from the space heating system served thereby. The combustion gases therefore enter and collect in the heated rooms and produce a condition deleterious to health and in some cases sudden death. It is therefore the main object of the present invention to provide a control for heating systems that will automatically cut off the supply of fuel to the fire of a space heater when dangerous or undesired draft conditions such as a poor up-draft, no draft, or back pressure occurs in the chimney stack and in the stack connections serving the heater. My control also utilizes a visual and/or audible signal to promptly Warn the occupants of the dangerous or undesirable draft conditions in the chimney for the heater.

Another object of the invention is to provide a reliable and inexpensive control that may be installed on' existing heaters at a minimum of cost and which will, upon failure of the chimney, instantly turn off the fuel to the heater fire and thus preclude the further escape of fumes from the combustion chamber of a heater into the heated room.

Other objects, advantages and novel features of the invention will be apparent from the following description and the accompanying drawings, in which:

Fig. 1 is a side elevation of a heating system embodying the control of this invention, parts thereof being shown in section.

Fig. 2 is a diagrammatic view of my control, parts thereof being detailed and shown in central section.

Referring to Fig. 1 of the drawing there is shown a heating system embodied in a space heater unit 5 having a gas burner 6 located within a combustion chamber 7. The burner is connected to a fuel supply pipe 8 through a normally open, shut-off valve generally indicated by the reference numeral 9. The combustion chamber of the heater unit has a pipe connection 10 with a chimney stack 11 for carrying olf flue gas and other products of combustion of the fire in the chamber, said pipe connection preferably having a T-fitting 12' interposed therein which is provided with a short conduit 13 that is open at its free end 14. As best shown in Fig. 2 the open end of the conduit has an imperforate damper 15 pivotally mounted thereon by a hinge 16 secured to the upper exterior part of the conduit and to the upper end portion of the damper in position such that the damper is normally suspended to close the open end 14 of the conduit by the influence of gravity.

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create a vacuum or negative pressure in the conduit 13' that forces the damper tighter against the open end 14 of the said conduit to effectively close the opening under all up-draft conditions existing in the chimney and the pipe connection. In the event an internal pressure con dition would develop within the pipe connection 10 because of a down-draft in the chimney stack or because of a block in the chimney stack and consequent delivery and accumulation of 'flue gases from the combustion chamber into the connection, such internal pressure,

however slight, will move the damper 15 outwardly to uncover the opening 14, such movement operating to close a first electric switch 17 comprising a fixed contact 18 mounted on a bracket 19 on the conduit and a movable contact 20 carried by the damper 15.

The shut-off valve 9 for the fuel line 8 is. detailed in Fig. 2 and comprises a resetting stem 21 mounted cen trally within an elongated chamber 22 for axial movement, the inner end of the stem being headed at 23 to mount a washer 24. The stem is continuously urged by spring 25 toward a position to engage the washer 24 against a seat 26 which when seated therea-gainst'will' close off the gase in supply line 8. An intermediate portion of the stem has a notch 27 formed therein for receiving the lower end of a vertical plunger rod 28 carried by the armature 29 of a solenoid 30 mounted upon the chamber 22. The stem has a knurled, reset knob 31 on its outer end.

A normally closed second switch 32 is preferably mounted on the chamber 22 and comprises a pair of resilient fingers 33-34 fixed to a mounting plate 35 and having contacts 36 and 37, respectively, on their lower end portions. A shoulder 38 is formed on the stem 21 in position to engage the lower end of finger 34 to break the contacts 36 and 37 and open the switch as the stem moves under the influence of spring 25 toward closed valve position. The switch may be enclosed in a suitable case 39, if desired.

As shown in Fig. 2 the first switch 17 and the second switch 32 are wired in series in an electric circuit comprising lines 40 and 41, a source of electricity for the circuit being supplied through power lines 42 and 43 interposed in line 41. An electric lamp signal 44 and/or an electric bell signal 45 are connected in parallel across the lines 40 and 41 in series with the source of electricity and the first switch 17 whereby the signals are electrically actuated when the switch 17 is in closed position.

In normal heater operation the fuel shut-off valve 9 will be in the condition shown in Fig. 2 with the washer 24 spaced away from seat 26 to allow fuel to flow through the line 8 to the fire in the combustion chamber 7 of the heater 5, the end of the solenoid plunger rod 28 being engaged in the notch to hold the stem in open position against the action of spring 25. The second switch 32 will be in the closed circuit position. Damper 15 will remain in position closing the opening 14 in the conduit 13 as long as normal and satisfactory draft conditions are maintained in the chimney stack and heater pipe connection 10 thus keeping the switch contacts 18 and 20 spaced apart in open switch position. However when undesirable or dangerous draft conditions prevail in the stack or pipe connection these conditions create an internal pressure in the connection which moves the damper 15 to open condition with respect to the opening 14, such movement closing the contacts of the first switch 17 which in turn completes the circuit to the solenoid 30. Energization of the solenoid disengages plunger 28 from the stem 21 thus permitting the spring 25 to move the washer against its seat 26 to close ofi Patented Nov. 17, 1959 3 the supply of fuel gas in line 8 thus extinguishing the fire in the combustion chamber 7 so that gas fumes cannot be evolved to thereafter enter the heated room. Movement of the stem 21 to closed valve position opens the contacts 36 and 37 of the second switch 32 thus deenergizing the solenoid and permitting the end of the plunger rod 28 to fall by gravity against a smooth part of the stem 21 in position to engage the notch 27 when the valve is reset by pulling out on the knob 31. It will be noted that the signals 44 and 45 will be actuated as long as the first switch 17 is in closed condition by reason of the open position of the damper 15.

What is claimed is:

1. An automatic control for a heating system, having a heater unit including a combustion chamber, means for supplying fuel to the fire in the combustion chamber, a, normally open fuel shutoff means, and a pipe connection between the combustion chamber and a chimney stack, the combination of a port formed in said connection opening to atmosphere, a pivotally mounted, gravity actuated damper-normally suspended to close the opening and adapted to open the port in response to internal pressure conditions within the connection, a normally open first switch closed by the opening movement of the damper, a solenoid for closing the shut-off means, a normally closed second switch opened upon closing of the shut-01f means, and a circuit including the solenoid, the first and second switches in series with a source of electric current.

2. An automatic control for a heating system, having a heater unit including a combustion chamber, means for supplying fuel to the fire in the combustion chamber, a normally open fuel shut-off means, and a pipe connection between the combustion chamber and a chimney stack, the combination of a port formed in said connection opening to atmosphere, a pivotally mounted, gravity actuated damper normally suspended to close the opening and adapted to open the port in response to internal pressure conditions within the connection, a normally open first switch closed by the opening movement of the damper, a solenoid for closing the shut-01f means, a normally closed second switch opened upon closing of the shut-off means, a circuit including the solenoid, the first and second switches in series with a source of electric current, and an electrically energized signal wired in the circuit in series with the source of electricity and parallel to the first switch.

References Cited in the file of this patent UNITED STATES PATENTS Field Sept. 4, 1956 

